Beneficial Insects

“Pollinators are responsible for 1 out of every 3 bites of food we eat” [Pollinator.org]

It is no secret that insects play an important part in Learning Gardens. At their worst, they can destroy an entire season’s harvest (and distract students in the garden) and at their best they are responsible for the production of fruits, vegetables, and flowers. In this post, we’ll review the good guys–beneficial insects–and how to attract them to our Learning Gardens.

Beneficial insects can be grouped in three categories:

  • pollinators
  • parasitoids, which feed off a host
  • predators

POLLINATORS

Common examples found in Los Angeles Learning Gardens:

  • bees: we have 1,600 species of bees in California—the most diverse of any state in the US–though not all are pollinators! Learn about CA Native bees via UC Davis.
  • butterflies and moths: there are 236 species and moths in LA County—not all are good for the garden! Those little white moths we commonly see in the garden, Cabbage Whites, will lay the eggs of hungry cabbage-loving caterpillars. Some common butterflies we find in LA Learning Gardens include:
    • Western Tiger Swallowtail: these large, yellow butterflies are common in urban areas as well as less developed locales
    • Monarch: if you maintain a garden year-round, please consider growing milkweed or other Monarch-attracting plants in your Learning Garden or at home!
    • Painted Ladies – one billion flew through LA County a few weeks ago!
  • flies: yes, certain species are pollinators. These include drone flies and syrphid flies and are both important pollinators and predators.

PARASITOIDS

Common examples found in Los Angeles Learning Gardens:

  • parasitic wasps (many species): these very small (usually less than 1/10”) wasps can attack insects directly and lay their eggs inside, eat pest eggs, or lay their own eggs in a pest egg. Parasitic wasps harm aphids, scale, and other small insects and are incapable of harming humans.
  • tachinid flies (many species): these small (between 1/3” and ¼”) insects that resemble houseflies lay eggs on an insect host where they hatch. Different species target different garden pests. These flies also act as pollinators!

PREDATORS

Common examples found in Los Angeles Learning Gardens:

A note about non-discriminating predators: these predators (praying mantis, assassin bugs, etc.) will eat both insect pests and other beneficial insects. If purchasing insects to release in your garden, we advise purchasing lacewings as they will only eat pests. We do not advise purchasing ladybugs for pest management as they tend to fly away.

 

ATTRACTING BENEFICIAL INSECTS

But how do you keep the beneficial insects around? It’s simply not enough to attract beneficial insects to your garden, you must also provide food (pests), moisture, and shelter so they’ll stick around. In addition to providing a balanced garden ecosystem, you should also:

 

PLANT A VARIETY OF FLOWERS AND HERBS

Plant a mix of flowers and crops to ensure you are attracting a variety of insects. Not all insects can pollinate all flowers and planting different plants will ensure more places for beneficial insects to live. Planting different flowers will also ensure there is always something blooming in your garden. Have an extra spot in your garden bed? Plant some flower seeds… or keep a few bolted plants in the garden! Leaving a few carrots, beets, radishes, onions, or broccoli plants just for the pollinators will keep them happy.

A lot of spring crops naturally flower (think tomatoes, peppers, eggplant, beans, etc.) but there is not much blooming in the fall. Plant flowers in or on the perimeter of your garden beds to attract nearby pollinators!

PLANT DENSELY

You can provide a great habitat for beneficial insects by simply planting more densely. One broccoli plant during the Santa Ana winds provides less protection than a densely planted bed full of multiple broccoli and flowers. This also helps protect the soil from blowing away!

 

PLANT CALIFORNIA NATIVES

There are many native pollinators that would love to visit your garden. Help your garden and help protect native insects by planting California native flowers and shrubs in green spaces around the garden. Native plants should not be grown in Learning Garden beds as they are not compatible with the needs of edible crops–edible crops need plenty of water while native plants need a lot less. However, planting native flowers and shrubs in an empty tree well, patch of soil, or large pot close to the garden will give you the benefit of both worlds.

The Theodore Payne Foundation has a lot of information about local plants, a retail nursery (in Sun Valley and online), school programs, and even a wildflower hotline.

Please note: many native plants should be planted in October.

MINIMIZE PESTICIDE USE

Pesticides not only attack pests but can also harm beneficial insects. This includes DIY (yes even soap and water mixes!), organic, etc. pesticides and not just conventional mixes! You can mitigate the risk to beneficial insects by:

  • rotating your crops. If you have an insect infestation on one of your crops, avoid planting similar crops in that bed. It is a smart idea to write down what pests you had in your Learning Garden’s Ed Layout (map). If you need a copy, ask your Garden Educator.
    • Example: if you have aphids on your string beans, avoid planting any legumes in that bed. Plant a different crop and a few flowers that attract aphid predators.
  • target specific insect pests. While broad-spectrum insecticides are very easy to use, using targeted methods of pest control will minimize damage to beneficial insects. You can use nematodes that only harm grubs, Bt (a soil bacteria) that target only insects that eat it, physical barriers, or other non-broad methods. These targeted measures will keep children, adults, wildlife, and insects safe!
  • use pesticides (including DIY, organic, etc.) as a last ditch effort. Commercial farmers that follow IPM (integrated pest management) practices have an acceptable level of crop loss in mind before they start spraying. They do this because no farm or garden will be 100% pest free and over-spraying causes more harm than good. In the meantime, you should remove infected branches, dislodge insects with strong sprays of water, etc. You can check the Directory of Least-Toxic Pest Control Products, which includes natural remedies as well.
  • check the National Pesticide Information Center to see what pollinator (and human) safe pesticides–this includes Bt (soil bacteria) and other organic gardening management options–are available.
    • Example: Neem tree oil is safe for birds, mammals, bees, and plants
  • spray smart. Spray on non-windy days, preferably in the evenings (when bees return to their hives), and when the high temperature is projected to be less than 90 degrees F (in order to prevent the leaves from burning–nothing to do with insects). Do not spray blooming plants or flowers!

Happy gardening! And remember, feel free to reach out to your Garden Educator if you have any questions!